/**
 *    Copyright (C) 2025-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#include "mongo/s/change_streams/collection_change_stream_db_present_state_event_handler.h"

#include "mongo/s/change_streams/collection_change_stream_db_absent_state_event_handler.h"

namespace mongo {

ShardTargeterDecision
CollectionChangeStreamShardTargeterDbPresentStateEventHandler::handleMoveChunk(
    OperationContext* opCtx,
    const MoveChunkControlEvent& event,
    ChangeStreamShardTargeterStateEventHandlingContext& ctx,
    ChangeStreamReaderContext& readerCtx) {
    // Open a cursor on the data shard 'event.toShard' if not already opened.
    const auto& currentlyOpenedShards = readerCtx.getCurrentlyTargetedDataShards();
    const bool isCursorAlreadyOpened = currentlyOpenedShards.count(event.toShard);
    if (!isCursorAlreadyOpened) {
        readerCtx.openCursorsOnDataShards(event.clusterTime + 1, {event.toShard});
    }

    // Close cursor on the data shard 'event.fromShard' if all chunks have been migrated from donor.
    if (event.allCollectionChunksMigratedFromDonor) {
        tassert(10917003,
                "cursor should have been opened",
                currentlyOpenedShards.count(event.fromShard));
        readerCtx.closeCursorsOnDataShards({event.fromShard});
    }

    return ShardTargeterDecision::kContinue;
}

std::unique_ptr<ChangeStreamShardTargeterStateEventHandler>
CollectionChangeStreamShardTargeterDbPresentStateEventHandler::buildDbAbsentStateEventHandler()
    const {
    return std::make_unique<CollectionChangeStreamShardTargeterDbAbsentStateEventHandler>();
}

}  // namespace mongo
